The present disclosure generally relates to volume filling mechanical structures utilized for controlled impact energy management. The volume filling mechanical structures are volumetrically reconfigurable such as to occupy a small volume when in a dormant state and rapidly expand to a larger volume in a deployed state upon activation by an activation mechanism.
Many strategies have been developed in the art of vehicle design for absorbing energy and attenuating impacts experienced by both vehicle occupants and pedestrians in motor vehicle impact events. As such, a vehicle, in addition to the inherent crush characteristics of its structure, may have various dedicated energy absorbing structures. Their function is to dissipate energy and limit forces and decelerations occupants/pedestrians experience in the event of an impact. In the vehicular arts, there are generally two types of such dedicated energy management structures: those that are passive, and those that are active.
An example of an energy absorbing structure that has been used in vehicles is an expanded honeycomb celled material, which is disposed in the expanded form within the vehicle environment. FIG. 1 illustrates a honeycomb celled material and its process flow for fabricating the honeycomb-celled material. A roll 10 of sheet material having a selected width W is cut to provide a number of substrate sheets 12, each sheet having a number of closely spaced adhesive strips 14. The sheets 12 are stacked and the adhesive is cured to thereby form a block 16 having a thickness T. The block 16 is then cut into appropriate lengths L to thereby provide so-called bricks 18. The bricks 18 are then expanded by physical separation of the upper and lower faces 20, 22, where adhesive strips serve as nodes to form the honeycomb cells. A fully expanded brick is composed of a honeycomb celled material 24 having clearly apparent hexagonally shaped cells 26. The ratio of the original thickness T to the expanded thickness T′ is between about 1:10 to about 1:60. The honeycomb celled material is then used in fully expanded form within the vehicle environment to provide impact energy management and/or occupant protection (through force and deceleration limiting) substantially parallel or at an acute angle with respect to the cellular axis. As noted, because the honeycomb material is used in the fully expanded form, significant vehicular space is permanently used to accommodate the expanded honeycomb material.
The expanded honeycomb celled material provides impact energy management parallel or at an acute angle with respect to the cellular axis at the expense of vehicular space that is permanently occupied by this dedicated energy management structure.
Energy absorbing structures often have a static configuration in which their starting volume is their fixed, operative volume, i.e. they dissipate energy and modify the magnitude and timing characteristics of the deceleration pulse by being compressed (i.e., crushing or stroking of a piston in a cylinder) from a larger to a smaller volume. Since these passive crash energy management structures occupy a maximum volume in the uncrushed/unstroked, initial state, they inherently occupy vehicular space that must be dedicated for impact energy management—the contraction space being otherwise unusable. Expressed another way, passive impact energy management structures use valuable vehicular space equal to their initial volume, which is dedicated exclusively to impact energy management throughout the life of the vehicle even though an impact may never occur, or may occur but once during that time span.
One major category of active energy absorbing structures includes those that have a predetermined size that expands at the time of an impact so as to increase their contribution to impact energy management. One type of such a dedicated volume/size changing active energy absorbing structure is a stroking device, basically in the form of a piston and cylinder arrangement. Stroking devices can be designed so as to have low forces in extension and significantly higher forces in compression (such as an extendable/retractable bumper system) which is, for example, installed at either the fore or aft end of the vehicle and oriented in the anticipated direction of impact induced crush. The rods of such devices would be extended to span the previously empty spaces upon the detection of an imminent impact or an occurring impact (if located ahead of the crush front). This extension could be triggered alternatively by signals from a pre-impact warning system or from impact sensors or be a mechanical response to the impact itself. An example would be a forward extension of the rod due to its inertia under a high G impact pulse. Downsides of such an approach include high mass and limited expansion ratio (1:2 rather than the 1:10 to 1:60 possible with a compressed honeycomb celled material).
Another example of a volume/size changing active energy absorbing structure is an impact protection curtain. For example, a roll down shade functions principally to contain the occupant within the vehicle. Containment is provided because the roll down curtain, while being flexible in bending when out of plane, is quite stiff in-plane.
Accordingly, there remains a need in the art for activation mechanisms for selectively deploying expandable energy absorbing devices used for impact attenuation, for structural reinforcement, and the like.